1. Field of the Invention
The present invention relates in general to a cylindrical upper support used in a suspension system of a motor vehicle, for elastically connecting a body of the vehicle and a piston rod of a shock absorber of the vehicle, and more particularly to such an upper support which is capable of effectively damping or isolating vibrations transmitted through the piston rod in its radial direction, or received in a transverse direction of the vehicle.
2. Discussion of the Prior Art
There is known a cylindrical vibration-isolating upper support of a type which is interposed between the piston rod of the shock absorber and the vehicle body, for elastically connecting the shock absorber and the vehicle body, such that the vibrations applied thereto are suitably damped or isolated. This type of upper support generally consists of a cylindrical or annular inner rigid member to which the piston rod of the shock absorber is fixed, a cylindrical outer rigid member which is disposed radially outwardly of the inner rigid member and fixed to the vehicle body, and an elastic body interposed between the inner and outer rigid members for elastically connecting the two members. The known upper support is adapted to damp or isolate the input vibrations applied between the piston rod of the shock absorber and the vehicle body, primarily based on elastic deformation of the elastic body which connects the inner and outer rigid members.
However, the known cylindrical upper support constructed as described above is limited in its vibration-isolating capability with respect to high-frequency vibrations received through the piston rod in the transverse direction of the vehicle, since the upper support utilizes only elastic deformation of the elasic body for damping or isolating the input vibrations. In this known arrangement, there arises a problem that the vibrations transmitted from the piston rod to toward the vehicle body through the upper support cause unfavorable noises which can be heard within the driver's and passengers' compartments of the vehicle.